I wash washing my 2009 Honda CRV this morning and noticed in the rear left fender well some of the black stuff (undercoating ?) was starting to come off in spots, showing what appears to be shiny metal underneath. What should I use to touch up these areas, and is there any special prep I should do? Thanks!
Undercoating coming off ?
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Undercoating in a can has held up for me since last fall. It's wax based and it dries tacky, not hard or firm. I haven't had any issues with chips or cracks from salt and rocks hitting the underbody. Prep-wise, if you have any large uncovered areas that have rust forming, you could just hit it with wire-brush and hose, wait for that to dry, and apply. although i think you can spray it right over rust.
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Originally Posted By: Enjoil
Undercoating in a can has held up for me since last fall. It's wax based and it dries tacky, not hard or firm. I haven't had any issues with chips or cracks from salt and rocks hitting the underbody. Prep-wise, if you have any large uncovered areas that have rust forming, you could just hit it with wire-brush and hose, wait for that to dry, and apply. although i think you can spray it right over rust.
Please don't.
Undercoating in a can has held up for me since last fall. It's wax based and it dries tacky, not hard or firm. I haven't had any issues with chips or cracks from salt and rocks hitting the underbody. Prep-wise, if you have any large uncovered areas that have rust forming, you could just hit it with wire-brush and hose, wait for that to dry, and apply. although i think you can spray it right over rust.
Please don't.
Originally Posted By: eljefino
Originally Posted By: Enjoil
Undercoating in a can has held up for me since last fall. It's wax based and it dries tacky, not hard or firm. I haven't had any issues with chips or cracks from salt and rocks hitting the underbody. Prep-wise, if you have any large uncovered areas that have rust forming, you could just hit it with wire-brush and hose, wait for that to dry, and apply. although i think you can spray it right over rust.
Please don't.
Yes I tried that once and the rust just kept spreading underneath. Stop the rust first.
Originally Posted By: Enjoil
Undercoating in a can has held up for me since last fall. It's wax based and it dries tacky, not hard or firm. I haven't had any issues with chips or cracks from salt and rocks hitting the underbody. Prep-wise, if you have any large uncovered areas that have rust forming, you could just hit it with wire-brush and hose, wait for that to dry, and apply. although i think you can spray it right over rust.
Please don't.
Yes I tried that once and the rust just kept spreading underneath. Stop the rust first.
The undercoating on my car was also starting to dry and crack, i removed the bits that were starting to come off and reapplied new underseal and that's it.
The easiest would be oil spray based in a can. It will creep into the broken sections and protect the exposed panels. However in a wheel well it will wash off and has to be re-applied at least annually. Twice a year would be preferable.
Personally, I would brush on bearing grease on the entire wheel well. It will resist washing off much better and still creep during summer months.
Personally, I would brush on bearing grease on the entire wheel well. It will resist washing off much better and still creep during summer months.
As best I could see there was no rust. I don't have a problem applying a coating twice a year. I suppose I will have to remove the wheel and inspect closer before I do anything.
What kind of undercoating is coming off?
In the US, the best undercoating is CarWell and Fluid Film. Both will penetrate rust. Apply yearly at a minimum.
In the US, the best undercoating is CarWell and Fluid Film. Both will penetrate rust. Apply yearly at a minimum.
Originally Posted By: Donald
What kind of undercoating is coming off?
In the US, the best undercoating is CarWell and Fluid Film. Both will penetrate rust. Apply yearly at a minimum.
I have no idea what kind it is, whatever came on the CRV from the factory?
What kind of undercoating is coming off?
In the US, the best undercoating is CarWell and Fluid Film. Both will penetrate rust. Apply yearly at a minimum.
I have no idea what kind it is, whatever came on the CRV from the factory?
Kestas
Staff member
That's a sound deadener. It becomes brittle and will trap corrodants once it starts to break up and delaminate. That's why they call it undercoating and not rustproofing.
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